| dc.description.abstract | This study aims to develop a laser direct writing technique for fabricating metal mesh transparent electrodes. The self-synthesized Ag-doped polyvinyl alcohol (PVA) nanocomposite is used for selective laser sintering, SLS. The nanocomposite is a mixture consisting of silver nitrate, AgNO3, and PVA. As irradiated by laser, the chelated Ag ions are first reduced from PVA and then aggregate into silver nanoparticles, Ag NPs. With appropriate operating parameters, laser power and scan speed, the reduced Ag NPs can be sintered into silver wires. The SLSed silver wires show good optical and mechanical properties and exhibit good conductivity, which can be used as flexible Ag mesh transparent electrodes. Within the current operating parameters, the sintered silver wire has a minimum line width of 5 μm, a peak height of about 300 to 400 nm and an optimum sheet resistance down to 10 times of the bulk silver. We investigate the microstructures of silver wires subjected to five laser powers of 20, 40, 60, 80, and 100 mW, respectively; and, each at five scan speeds of 0.1, 0.3, 0.5, 0.7, 1.0 mm/s. Results show that the scan speed has a more significant effect on the microstructure and quality of silver wires. Based on the relatively optimum operating condition of laser, the best sintered Ag mesh has the features: sheet resistance is less than 19 Ω/sq and transmittance is larger than 85%, no less favorable than commercial metal oxide electrodes. The height of Ag lines range from 300 to 400 nm, which is still too high, especially for organic optoelectronic devices where the thickness of organic film is often between tens to hundreds of nanometers. To fabricate a metal mesh electrode with a very low surface roughness, the sintered silver mesh on the glass substrate was embedded in a polyimide film to produce a flexible embedded Ag mesh electrode. To examine the stability in conductivity, we conduct a cyclically tensile loading test on the flexible Ag mesh substrate. Results show the sheet resistance is increased from 19 to 24 Ω/sq, an increase of 24%, after 5000 cycles of loading where the substrate is bended at a radius of curvature of 5 mm. The sintered Ag mesh electrode is finally used as the cathode of a white light OLED to demonstrate its feasibility to replace the usual transparent metal oxide electrode. | en_US |